Re: [v5] ASoC: qcom: lpass-cpu: Fix pop noise during audio capture begin
From: Doug Anderson <dianders@chromium.org>
Date: 2021-06-03 22:42:11
Also in:
alsa-devel, linux-arm-msm, linux-devicetree
Judy, On Thu, Jun 3, 2021 at 8:08 AM Judy Hsiao [off-list ref] wrote:
quoted hunk ↗ jump to hunk
@@ -315,12 +353,54 @@ static int lpass_cpu_daiops_trigger(struct snd_pcm_substream *substream, return ret; } +static int lpass_cpu_daiops_prepare(struct snd_pcm_substream *substream, + struct snd_soc_dai *dai) +{ + struct lpass_data *drvdata = snd_soc_dai_get_drvdata(dai); + struct lpaif_i2sctl *i2sctl = drvdata->i2sctl; + unsigned int id = dai->driver->id; + int ret; + /* + * Ensure lpass BCLK/LRCLK is enabled bit before playback/capture + * data flow starts. This allows other codec to have some delay before + * the data flow. + * (ex: to drop start up pop noise before capture starts). + */
nit: there's usually a blank line between the variable declarations and the first line of code, even if the first line of code is a comment.
+ if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+ ret = regmap_fields_write(i2sctl->spken, id, LPAIF_I2SCTL_SPKEN_ENABLE);
+ else
+ ret = regmap_fields_write(i2sctl->micen, id, LPAIF_I2SCTL_MICEN_ENABLE);
+
+ if (ret) {
+ dev_err(dai->dev, "error writing to i2sctl reg: %d\n", ret);
+ return ret;
+ }
+
+ /*
+ * Check mi2s_was_prepared before enabling BCLK as lpass_cpu_daiops_prepare can
+ * be called multiple times. It's paired with the clk_disable in
+ * lpass_cpu_daiops_shutdown.
+ */
+ if (!drvdata->mi2s_was_prepared[dai->driver->id]) {
+ drvdata->mi2s_was_prepared[dai->driver->id] = true;
+ ret = clk_enable(drvdata->mi2s_bit_clk[id]);
+ if (ret) {
+ dev_err(dai->dev, "error in enabling mi2s bit clk: %d\n", ret);
+ clk_disable(drvdata->mi2s_osr_clk[id]);Can you explain why this clk_disable() is here? Your function didn't turn this clock on, so why should it be turning it off in the error case?
+ drvdata->mi2s_was_prepared[dai->driver->id] = false; + return ret; + }
Why not put the `drvdata->mi2s_was_prepared[dai->driver->id] = true;` _after_ you check for errors. Then you don't need to undo it in the error case. I presume that your prepare() function isn't reentrant and can't be called at the same time as your shutdown (right?). Other than that, I don't have any objections to this patch anymore. I probably won't add a formal "Reviewed-by", though, since I _really_ don't know anything about the issue at hand or the code. I just stumbled upon this because I was getting the clock splat at bootup. If someone feels like this needs me to spin up enough to understand / really review this patch then please yell. -Doug _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel